Polyvinylpyrrolidone for improved optical brightener absorption for durable press cellulosic fabrics

ABSTRACT

Durable press fabrics possessing the improved ability to absorb optical brighteners during laundering have been prepared. Repeated launderings with detergents which contain these optical brighteners increase the whiteness with each laundering. This quality is imparted to cotton and other cellulosic fabrics when polyvinylpyrrolidone is incorporated in a crosslinking formulation.

United States Patent Blanchard et al.

'[151 3,658,457 51 Apr. 25, 1972 POLYVINYLPYRROLIDONE FOR IMPROVED OPTICAL BRIGHTENER ABSORPTION FOR DURABLE PRESS CELLULOSIC FABRICS Inventors: Eugene J. Blanchard, New Orleans;

Robert J. Harper, Jr.; Gloria A. Gautreaux, both of Metairie; John D. Reid, New Orleans, all of La.

The United States of America as represented by the Secretary of Agriculture Filed: Jan. 7, 1971 Appl. No.: 104,783

Assignee:

U.S. Cl ..8/ll)0, 8/115.6, 8/116.3,

Int. Cl ..D06m 15/58, D06m 15/36 Field ofSearch ..8/ll6.3,115.6,1l6.2, 85, 8/100 References Cited OTHER PUBLICATIONS Holmes et aL, American Dyestuff Reporter, September 26, 1955, P702- P704 Hansen et a1, American Dyestuff Reporter, February 1, 1954, P72- P75 Primary Examiner-George F. Lesmes Assistant Examiner-J. Cannon Anorney-R. Hoffman and W. Bier [5 7] ABSTRACT 1 Claim, N0 Drawings POLYVINYLPYRROLIDONE FOR IMPROVED OPTICAL BRIGHTENER ABSORPTION FOR DURABLE PRESS CELLULOSIC FABRICS A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to fabrics treated with polyvinylpyrrolidone. More specifically this invention relates to the incorporation of polyvinylpyrrolidone in a crosslinking formulation bath in order to impart to cotton or other cellulosic fabrics the qualities of durable press and the ability to absorb optical brighteners from detergents during laundering.

The main object of this invention is to provide a method by which cotton and other cellulosic fabrics can be processed by ordinary methods so that they will acquire the improved desirable quality of being able to absorb optical brighteners from detergents upon laundering, as well as durable press properties.

Another object of this invention is to accomplish the first object with an element of permanency. Both objects have been accomplished, and the finished fabrics have the durable press properties and the ability to absorb optical brighteners from detergents, so that treated fabrics tend to be further whitened with repeated launderings.

Heretofore normally crosslinked durable pressed or washwear fabrics have had a small capacity for renewing their whiteness by absorbing the optical brighteners from wash solutions containing everyday laundry detergents. It has been common practice to try to overcome this deficiency by adding the optical brightener to the crosslinking solution, but this approach has definite deficiencies. Firstly, the basic chemical nature of many optical brighteners limits their application because they tend to neutralize the acid catalyst. This leads to a poor durable press appearance. The second limitation is that the high temperatures used in curing lead to loss of activity by the brightener. Lastly, discoloration or graying in the fabric may occur in time, due to leaching in laundering or destruction of the brightener by light or chemical bleaching agents.

We have now found that by incorporating a certain amount of polyvinylpyrrolidone in the pad bath it is possible to producedurable press or wash-wear fabrics which will absorb the optical brighteners in laundering using common detergents. The polyvinylpyrrolidones used to accomplish this improvement in fabric whiteness have the accompanying structure,

oar-on,

wherein n can be a number of repeating units of about from 45 to 4,500.

Although the polyvinylpyrrolidone is water soluble and is not chemically bound to the fabric, sufficient polymer is trapped in the fabric to maintain its effect in improving fabric whiteness after a number of launderings. Thus, after laun- 'derings, a cotton fabric treated with a crosslinking formulation containing a polyvinylpyrrolidone was noticeably whiter than a similar fabric treated with the sameformulation without this additive reactant. Another means by which the effect of polyvinylpyrrolidone can be demonstrated is by inspection of the fabrics under ultraviolet light. Under these conditions, a cured fabric prepared from sensitized fabric treated in a conventional manner, was gray. On the other hand, the sample prepared from sensitized fabric treated with a solution containing the polyvinylpyrrolidone was white under ultraviolet light. This reflects the ready absorption of optical brighteners to the latter fabric. These results were readily observed on fabric washed as many as 10 times, thus illustrating the durability of this treatment.

In addition to the observation of improved optical brightener absorption and hence fabric whiteness under either regular or UV light, a method has been developed to measure the relative improvement in absorption of brightener by the polyvinylpyrrolidone treated fabrics. In this method, a series of fabrics including an untreated cotton, a crosslinked cotton without polyvinylpyrrolidone, and a crosslinked cotton with polyvinylpyrrolidone are laundered with a detergent containing optical brightener. Then, the fluorescence of these samples is measured at the maximum corresponding to optical brightener fluorescence. The values are expressed on a percentage basis with the untreated cotton given the arbitrary value of 100 percent. Under these conditions, the crosslinked cotton had a value of 24 percent and the crosslinked cotton samples with polyvinylpyrrolidone had values ranging from 74 to 88 percent with from 1 to 4 percent polyvinylpyrrolidone in the finish.

Another variation is possible with precured fabric. For this purpose, the precured fabric is given-an afterwash in a solution containing an optical brightener. Under these conditions, the washed fabrics treated with crosslinking agent and polyvinylpyrrolidone or fabric treated with crosslinking formulation, optical brightener and polyvinylpyrrolidone appeared whiter than the control fabrics treated with the same formulations, which did not contain polyvinylpyrrolidone.

in general, the process of this invention is the incorporation I of the polyvinylpyrrolidone in normal pad bath solutions to produce wash-wear or durable press cotton. From this point on, the fabrics are finished in a standard manner according to contemporary textile practice. This method can be used with a number of textile formulations, the only requirement being that a certain amount of water be replaced with an equivalent amount of polyvinylpyrrolidone. For precured fabrics, the modification of using an optical brightener in the afterwash or as a component in a solution in a second afterwash represents some variation from current textile practice on precured fabric.

Another process has been developed to improve the durability of the polyvinylpyrrolidone on the fabric. in this process, a polymer, such as a polyacrylate, is incorporated which polymer normally possesses good durability in multiple launderings. The finishing formulation, then, consists of a mixture of the standard crosslinking resin formulation, polyvinylpyrrolidone and the added polymer (polyacrylate). Fabrics finished with this combination show improved relative fluorescence after a number of launderings. Experiments using various polyacrylates suggest that polyacrylates with lower glass transition temperatures are more effective in promoting higher fluorescence values after multiple launderings than are polyacrylates with higher glass transition temperatures.

Polyvinylpyrrolidone of varying molecular weight was investigated to see whether fabric properties were influenced differently due to the change in molecular weight. With respect to the absorption of optical brightener, no great difference was noted for polyvinylpyrrolidone with molecular weights of approximately 10,000, 40,000, 160,000, and 360,000. However, the lower molecular weight polymers were slightly more effective. With respect to fabric hand and smooth drying characteristics, the high molecular weight additives causes a stiffening of the fabric and a slight loss in smooth drying performance. From this viewpoint, the lower molecular weight additives'5-40,000 would then seem to be preferred because they do not stiffen fabric or reduce durable press ratmg.

The polyvinylpyrrolidone is effective in pad bath concentrations ranging from about l percent to about 15 percent. The preferred range of polyvinylpyrrolidone concentration for overall performance appears to be from 1 percent to about 5 percent.

The following examples are intended to be representative of treating solutions rather than limiting. Numerous variations are obvious to those practiced in the textile arts.

A solution was prepared using 8 parts dimethylol dihydroxyethyleneurea, 0.5 parts zinc nitrate hexahydrate and 91.5 parts water. This mixture was padded onto a cotton printcloth, dried 7 minutes at 60 C., and cured minutes at 130 C. Four other samples were likewise treated in an analogous manner except that the padding mixture was 8 parts dimethylol dihydroxyethyleneurea, 0.5 parts zinc nitrate hexahydrate, 2 parts of polyvinylpyrrolidone and 89.5 parts water. For each sample, a polyvinylpyrrolidone of different molecular weight was used. The particular molecular weights were approximately 10,000, 40,000, 160,000, and 360,000. These samples together with an untreated cotton printcloth were then laundered using a laundry detergent containing optical brightener. The untreated cotton and the samples from the treatments containing polyvinylpyrrolidone were noticeably whiter than the sample crosslinked with no polyvinylpyrrolidone present. Under UV light, the samples with the polyvinylpyrrolidone on them were white while the crosslinked control appeared gray. When small samples of these fabrics were examined using a Farrand Spec- These data demonstrate clearly the advantages of using the polyvinylpyrrolidone in the finishing formulations. After both the first and 10th wash, the samples containing polyvinylpyrrolidone were distinctly whiter than the crosslinked control, which did not contain polyvinylpyrrolidone.

EXAMPLE 3 A series of -50 polyester-cotton fabrics was treated in a manner analogous to that described in Example 1. The principal difference was that varying amounts of polyvinylpyrrolidone were used in the padding formulations. A summary of treatments and properties of the resulting blended fabrics are reported in Table II. From these data, it is apparent that an improvement in optical brightener absorption was achieved by the use of polyvinylpyrrolidone in the finish. The high initial fluorescence value of the polyester-cotton control reflects the fact that brightener was used in the polyester melt. The loss of brightener from the fabric on washing is readily seen by the sharp drop in the relative fluorescence values from the first to the 10th wash for both the untreated polyester-cotton and the crosslinked polyester-cotton.

TABLE II.EFFECT OR POLYVINYLPYRROLIDONE ON BRIGHTENER ABSORPTION ON 50-50 POLYESTER-COTTON l Dimethylol dihydroxyethyleneurea.

1 Polyvinylpyrrolidone.

3 Conditioned wrinkle recovery angle.

4 A wash method was employed in which detergent containing brightener was used only in the first and tenth wash cycle.

6 Untreated polyester-cotton.

0 Untreated cotton.

trofluorometer, the crosslinked control without polyvinylpyrrolidone had a relative fluorescence value of 16 percent compared to 53 to 57 percent for the samples with polyvinylpyrrolidone.

EXAMPLE 2 A series of cotton fabrics was treated in a manner analogous to that described in Example 1. The principal difference was that varying amounts of polyvinylpyrrolidone were used in the padding formulations. A summary of treatments and properties of the resulting fabrics is given in Table I. From the data given in this table, it can be noted that increasing the amount of polyvinylpyrrolidone in the different formulations leads to higher relative fluorescence values not only for the samples after the initial wash but after the 10th wash.

EXAMPLE 4 Two series of cotton printcloth were treated in a manner analogous to that employed in Example 1. In one series, the fabrics were treated with DMDHEU and polyvinylpyrrolidone. In the other, the fabrics were treated with dimethylol dihydroxyethyleneurea, polyvinylpyrrolidone, and a polyacrylate. A summary of treatments and properties of the resulting blended fabrics are reported in Table [I].

TABLE I.-Efl'eet of polyvinylpyrrolidone on brightener absorption Relative fluorescence 4 Treatment, parts Condfi Mol. WRA 1st 10th Zn(NO3)zwt., (W+F) wash, wash. DMDHEU l (EH20 2O PVP 2 M (deg.) percent percent llhnethylol dihydroxyethylenenren. 1 Iolyvinylpyrrolldone. 1 Conditioned wrinkle recovery angle.

in the first and tenth wash cycle.

5 Untreated cotton.

LATE ON BRIGHTENER ABSORPTION Relative fluorescene 4 Treatment, parts nd.

WRA 1st 10th Zn (N002. Poly- (W+F) wash, wash,

DMDHEU 1 fiHzO H20 PVP Z acrylate 3 (deg) percent percent l Dimethylol (lihdroxyethylcnaurea. 2 PVP mol. wt. is 360,000. 3 lolyacrylate glass transition temperature is 0 C. Detergent containing brightenor was used in each laundering. 5 Untreated cotton. t

From these data, it is apparent that the use of a combination of polyvinylpyrrolidone and polyacrylate in a finish leads to an improvement in optical brightener absorption not only after the initial wash but also after the tenth wash. For example, the samples treated with dimethylol dihydroxyethyleneurea and polyvinylpyrrolidone had relative fluorescence values ranging from 65-74 percent after the first wash and 49-56 percent after the th wash. By contrast, with dimethylol dihydroxyethyleneurea, polyvinylpyrrolidone and polyacrylate, the relative fluorescence values ranged from 86 to 98 percent after the first wash and from 64-76 percent after the 10th wash. The polyacrylate used in this case had a glass transition temperature of 0 C. These results indicate that a combination of polymers can be employed in a finish to improve fabric whiteness both initially and after a number of launderings.

We claim: 1. A process for imparting to cellulosic fabrics improved optical brightener absorptivity comprising:

a. impregnating the cellulosic fabric with a solution containing about from 4% to of dimethylol dihydroxyethyleneurea, about from 0.1 to 3.0 percent of an acid catalyst, and about from '1 to 15 percent of a polyvinyl? pyrrolidone polymer having the structure:

CHr--CH:

(llHz-C 112T 

